use strict;
use warnings;
use JSON;

my $string  = read_json();
my $hashref = decode_json($string);

for my $item (@{ $hashref->{items} })
{
    if (exists $item->{orderItemTitle})
    {
        printf "Order Item Title: %s\n", $item->{orderItemTitle};
    }
}

sub read_json
{
    my $string =<<'EOS';
{\"order\\\\.shipTo\\\\.country\":\"US\",\"euddAccepted\":false,\"isFreeCart\":false,\"discount\
...
< most of input string omitted here >
...
\"hasAnyDelayedDeliveryItems\":false,\"addOnSubtotal\":\"$0.00\",\"story\":\"FCF6F91A\"}
EOS

    $string =~ s{ \\" }{"}gx;

    return $string;
}